1. Field of the Invention
This invention relates to semiconductor devices and more particularly to semiconductor devices formed in silicon films which are epitaxially deposited on an insulating substrate.
2. Prior Art
Integrated circuits are frequently used as modules in a large system such as a data processing system. In such applications, it is necessary that integrated circuits drive the following succeeding stages. In integrated MOS circuits, such as SOS-MOS circuits, the individual component elements are arranged in silicon films which have been epitaxially deposited on an insulating substrate. In such devices, the problem arises that a high output load may lead to a delay time of such magnitude that the upper frequency limit provided by the unloaded integrated circuit can no longer be attained.
With output stages having relatively large MOS transistors with short channel lengths, the problem can be solved only with use of a large amount of space. Bipolar transistors, however, have a high enough frequency response and are suited to larger output loads.
A disadvantage of such bipolar transistors arises since it is difficult to manufacture such transistors with sufficient current amplification due to the minute diffusion length of minority charge carriers in thin silicon layers.